Switched Beam Array

switched beam array[image source: Nallatech]

Adaptive Beam Array

adaptive beam array[image source: Nallatech]

They are meant to have a fixed beam shape, which is steerable [left
figure] or they have adaptive beam forming [right figure], in order to
direct their radiation on the desired target and avoid interferers.

"Reconfigurable antennas" are meant to reconfigure themselves in terms
of some parameters such as the radiation pattern, polarization, or
operating frequency. Early works focused on reconfiguration of (only)
one parameter. Naturally, later works had proposed reconfiguration of
more than one parameter.

Challenge

Whatever the approach, current solutions are based on the premise that all elements of the antenna array are fully operational.
However, if any element of the system fails,
the original characteristics of the system will degrade, possibly
severely. The user is then affected by that situation until the problem
is fixed, which can bear loss of service and high costs, especially for
spaced-based systems.
Let's see some examples of pattern degradation due to element failure
(by the "element failure" we don't just mean the sole failure of an
antenna, but a failure along the path to the antenna (e.g. in the cable
or in the splitter) that prevents the antenna to deliver the radiation
according to the original design):

Example 1.

let the array from the figure above comprise 4 dipoles and a radiation pattern as shown in the figure below

let's observe the same pattern from the side and the top: 2 main lobes and nulls between them

All array elements working properly - side view

All array elements working properly - top view

Now, if array element #3 fails (dipole arms disappear in the upper
figure), the pattern gets deformed, as shown in the figures below:

besides 2 original lobes, 2 parasitic lobes are created as the result of element failure

2
parasitic lobes eventually radiate in the directions they are not meant
to and create interference to other systems, or, simply, waste part of
the input power

Second array element failed - side view

Second array element failed - top view

Example 2.

A more detailed quantitative measure of array radiation degradation can be observed by 1D plot, as shown next.

the original (1111) has 1 main lobe and 2 suppressed back lobes

failure of element #3 (1101) causes back lobes to become major radiation, while formerly a major lobe is now suppressed

failure of element #4 (1110) here produces wider major lobe of the
original level and (only) 1 back lobe of a level higher than before

This is a small, 4-element array, with a simple radiation pattern and
small number of possible failure combinations (e.g. 1101, 1110, and
1010) that lead to pattern degradation. The point was to demonstrate
the principle of pattern degradation and imply how serious this can be
in case of large arrays and/or more subtle beam shapes.

So, the question is: How do we efficiently recover the system if part of it fails...
... on a hard-to-reach location, or
... at a critical moment?

Objectives

Our objective here is to develop a solution which will enable
antenna system to recover itself if failure of any element occurs. This
new kind of antenna we refer to as self-recovering or self-adaptive antenna system.

We plan to do a seamless integration of real-time computing and system optimization utilizing advanced hardware and software.

If success, this could be a predecessor to a broad range of future self-adaptive components, module, and systems.

The solution will bring improved reliability and versatility to systems and substantial cost-savings.

While the antenna system is meant to operate autonomously,
the user will retain control over the system by means of monitoring and
remote control. In the extension of this solution, we would be able to
adapt the system not only when something fails, but also to attain new
characteristics even when everything is healthy.

This solution will be significant for all systems where it
is sought to have intelligent operation and immediate response of an
antenna system to a sudden failure or to a change of conditions in the
surrounding environment. Such situations can readily appear in the
critical fields of today's technology, such as broadcasting,
transportation, defense, security, and the emerging field of
telemedicine.